They can both do it all on both ends of the ice, as both are great defensively every night no matter what.
If Mika has a bad night offensively it's because he's just a little off or unlucky. If Barky has a bad night offensively it's because he chose not to shoot or chose to not sacrifice defense for offense. Both appear to happen just as often as the other.
Objectively, yes- Barkov is by far and away the most talented, surely no argument from me there. It's my opinion that he's 2nd only to McDavid there. But we know that's not everything in a team game, so I feel choosing one or the other is entirely subjective and dependant on the rest of the team and flow of the game. Both will be a threat to put 3-5 pts up in any combination on any given night, so to me- wash.